An optical fiber (e.g., glass, plastic) carries light along its length. Light is kept in the core of the optical fiber by internal reflection. The optical fiber acts as a waveguide. Optical fiber can be used as a communication medium for telecommunication and networking applications because it is flexible and can be bundled into cables. Although referred to as “optical fiber,” optical fiber is not restricted to communicating light in the visible spectrum, and may transmit light signals of higher, or lower, wavelengths.
Optical fiber is especially advantageous for communications because light propagates through the fiber with less attenuation than for electrical signals using metal wires. This facilitates long distance communications using few repeaters. Unlike electrical communication modes, light signals are immune to electromagnetic interference, thereby eliminating cross-talk between signals and the effects of environmental noise. Non-armored optical fiber cables do not conduct electricity, which makes optical fiber a good solution for protecting communications equipment located in electrically-exposed environments, including communication structures prone to lightning strikes.
Optical fiber permits transmission at higher bandwidths (e.g., data rates) than other forms of communications. Per-channel light signals propagating in the fiber can be modulated at rates in the range of gigabits per second. An individual optical fiber can carry many independent channels, each using a different wavelength of light and wavelength-division multiplexing (WDM). Optical fiber saves space in cable ducts because a single optical fiber can carry much more data than a single electrical cable.
A fiber optic cable is usually made up of many individual optical fibers. For example, according to one commercially available configuration, twelve (12) 250 micron optical fibers may be grouped together in a buffer tube. A fiber optic cable may contain 6 buffer tubes (i.e., for a total of 72 optical fibers) and one or more strength members (e.g., metallic member), with the buffer tubes and strength member being surrounded by a jacket providing physical and environmental protection. Other commercially available fiber optic cable configurations may include 144 optical fibers (e.g., 12 buffer tubes of 12 optical fibers each), or 288 optical fibers (e.g., 12 buffer tubes of 24 optical fibers each), and ribbon fibers, among others.
Individual optical fibers (e.g., glass, plastic) can be fragile, and require measures to prevent fracturing, or breakage. Optical fiber can be subject to physical routes limited to a minimum bend radius, at the cable level and/or at an individual fiber level, to prevent fracturing, breakage, or signal distortions/losses. In addition, optical fibers may be damaged if they are subjected to excessive tension or physical impact. Due to the risk of damage, it is preferable to avoid handling individual fibers any more than is necessary.
Optical fibers are increasingly being used to provide signal transmission between various service providers (e.g., telephone systems, video systems, computer network, etc.) and individual users (e.g., homes, businesses). Fibers which support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those which can only support a single mode are called single-mode fibers (SMF). MMF generally has a larger core diameter, and is used for short-distance communication links, and SMF is used for longer distance communication links. Working with optical fiber (e.g., splicing, splitting, patching) involves close tolerances, and is best accomplished in controlled environments where physical alignments, temperature, and cleanliness are better managed to facilitate precision work results.